We have a regatta at the venue in June every year. I would guess the water temperature would be about the same at the end of July. I don't know what the actual temperature is, but I can tell you that my crew and I get cold really easy and we typically wear a farmer john wetsuit with a spray top. If it is cold (air temp rather than water) we wear a thermal shirt under the spray top. I think bootys would be optional depending on whether you like to sail in shoes or not. You will see some people wearing shorty wetsuits and some wearing goretex drysuits with shorts and tshirts underneath at that time. I should say that I wear a wetsuit and spray top for almost all of our events and the conditions have to be "frostbiting" or Africa hot for me to wear anything different.

Heck, the Alameda buoy shows the water is warmer than 60 deg F right now!
http://www.nodc.noaa.gov/dsdt/cwtg/cpac.htmlOk - so 60.1 deg F is not much over 60 . . .
There is a little almanac on the link above that shows average water temperatures in July/August will be about 66 deg F. That is 6 to 10 degrees warmer than blue water ocean in the area. Come on in, the water is fine.

I went out yesterday and wore trunks and a lifevest. We sailed on a reach SW from Crown Memorial Beach in Alameda to halfway across the bay and never got cold. In fact, the spray of the water from the hulls didn't make a difference in our comfort. However, air temps around the SF bay can be fickle, so bring something warm, especially for when the sun goes down.